Nutrition Essentials: Vitamins

Transcription

1 Nutrition Essentials: Vitamins Section 1 Welcome SLIDE # 1: Welcome to the module, Nutrition Essentials: Vitamins. In this module, you will have the opportunity to learn more about vitamins what they are and why they are so important for proper function of the human body. This module is approximately one hour in length. This course will be presented in a voice-narrated format that allows you to follow along with a PowerPoint slide presentation. A high-speed Internet connection is required to complete Nutrition Essentials. Content for this module, Nutrition Essentials: Vitamins, is divided into multiple sections (see menu bar on the left for course outline), enabling you to complete and/or review content at your own pace. Printable handouts, if applicable, will be presented prior to the section they are referenced. In the next section, you will be directed to complete a brief, multiple-choice pre-learning assessment. Once you have completed the pre-learning assessment, you will be free to advance the course by checking the Next Section button at the bottom of the page. At the conclusion of this module, you will be directed to complete a post-learning assessment that will determine if you successfully pass the course. If at any time, you wish to take a break from the module, simply log out and return to the course when you are ready to continue. When you sign back into the module, you will be taken directly to the section where you left off. To review a section you have already completed, click on the desired section on the left menu bar. Section 2 Learning Objectives The learning objectives for Nutrition Essentials: Vitamins are as listed below. At the conclusion of this module, participants will be able to: describe the definition of a vitamin; list the 14 known vitamins; describe how vitamins are classified; identify functions, food sources, deficiencies, and toxicities associated with each of the fat-soluble vitamins; and identify functions, food sources, and deficiencies associated with key water-soluble vitamins. Section 3 Introduction SLIDE # 2: Welcome to the Vitamins module of Nutrition Essentials. By now, you ve learned about carbohydrates, protein, and fat. Compared to these three nutrients, our bodies need vitamins in very small amounts, so they are termed micronutrients.

2 SLIDE #3: During this module, we ll provide a definition for vitamins and discuss the function of several vitamins, including B12, folate, and vitamins E, K, C, A, and D. In addition, we ll cover food sources for each vitamin, as well as their related deficiencies and toxicities. Section 4 Understanding Vitamins SLIDE #4: Let s first discuss the definition of a vitamin. Vitamins are described as: Organic compounds that are distinct from carbohydrates, fats, and proteins; Essential in small amounts for maintenance, growth, development, and reproduction; Not produced by the body in amounts that are adequate to meet normal physiological needs; Not containing calories, or energy; Natural components of foods that are usually present in small amounts, such as milligrams or micrograms; and Causing a specific deficiency syndrome if not consumed in adequate amounts. SLIDE # 5: The discovery of vitamins led to the field of nutrition. For example, long ago, Egyptian and Greek doctors were able to link the consumption of liver to curing night blindness, which is a condition related to vitamin A deficiency. Today, scientists have identified 14 known vitamins from food sources. Each of these vitamins is important for proper body function. These 14 vitamins include: vitamins A, C, D, E, and K; Thiamin, Riboflavin, Niacin, vitamin B6, folate, vitamin B12, Pantothenic Acid, Biotin, and Choline. During this presentation, we ll be discussing the vitamins listed in green. SLIDE # 6: The 14 vitamins can be classified into two groups: water-soluble and fat-soluble vitamins. Their classification depends on how they dissolve and how they re transported in the body. Fat-soluble vitamins dissolve in fat. Then, they re carried through the bloodstream, attached to substances within the body that are made with lipids, or fat. In fact, we need to consume moderate amounts of healthy fat in our diets so that we re able to absorb these vitamins. There are only four fat-soluble vitamins: A, D, E, and K. These vitamins can be stored in body fat, so consuming too much of them for a long period of time can be harmful to your health. In fact, high levels of vitamins A and D have been linked to toxicity, which leads to negative health effects. The water-soluble vitamins, B12, C, and folate, dissolve in water. These vitamins are transported in the bloodstream and are not stored in the body in significant amounts. The body uses what it needs of these vitamins, and the rest is excreted through urine. Therefore, individuals need to eat these vitamins on a regular basis. A quick word of caution, however: although water-soluble vitamins are not stored in the body, moderation in still the best approach. For example, taking high doses of water-soluble vitamins can be harmful to your kidneys.

3 Section 5 Fat-Soluble Vitamins: Vitamin A SLIDE #7: During the next few slides, we ll learn more about some specific vitamins. First, let s talk about vitamin A. Vitamin A, as we ve already learned, is a fat-soluble vitamin. Some important functions of vitamin A are that it promotes: normal vision and helps individuals see in low levels of light; normal bone and tooth development; the growth and health of cells and tissues in the body, especially skin; normal reproduction and development of a maturing embryo; and a healthy immune system, which fights infections. In addition to these functions, carotenoids, such as alpha and beta carotene that form vitamin A, can function as antioxidants and may reduce the risk for certain cancers. SLIDE #8: There are both plant and animal sources of vitamin A. In animal sources, vitamin A is completely formed and is referred to as pre-formed vitamin A. Foods such as liver, fish, eggs, and fortified milk are good animal sources of vitamin A. Some plant-based foods provide carotenoids, which the body can use to make vitamin A. These carotenoids are referred to as pro-vitamin A carotenoids. Red, yellow, orange, and dark-green leafy vegetables are good sources of carotenoids. SLIDE # 9: If an individual doesn t consume enough vitamin A, a deficiency can result. One of the early signs of a vitamin A deficiency is night blindness. Night blindness is the inability to adapt from a bright light or glare to being in darkness. This results in poor vision in low light conditions. If the deficiency persists, additional symptoms such as increased infections, dry, scaly, rough skin, problems with reproduction, diminished immunity, poor growth, blindness, and possibly death can result. The resulting deficiency disease from lack of vitamin A is called xerophthalmia [zeer-of-thal-mee-uh]. Vitamin A deficiencies can be common in developing countries but are rare in the United States. SLIDE # 10: Because vitamin A is stored in the body, consuming high doses of it over time can lead to toxicity. Some effects of vitamin A toxicity include birth defects, liver damage, nerve damage, reduced bone mineral density, headaches, dry and scaly skin, vomiting, and appetite loss. Most toxicity results from high intakes of vitamin A via dietary supplements. However, consumption of carotenoids from fruits and vegetables is considered safe. The body slows its conversion of carotenoids to vitamin A when the body stores are full. High carotenoid intakes can turn skin yellow. Section 6 Fat-Soluble Vitamins: Vitamin D SLIDE # 11: Vitamin D, which is also known as the sunshine vitamin, is a fat-soluble vitamin that serves several important functions in the body. Some of the functions of vitamin D include:

4 promoting the absorption of calcium and phosphorus and regulating how much calcium remains in the bloodstream; in fact, vitamin D may help prevent osteomalacia, and along with calcium, osteoporosis; promoting the formation of healthy bones and teeth; regulating cell growth; and promoting proper immune function. SLIDE #12: Very few foods in nature contain vitamin D. The best sources are beef liver, egg yolks, cheese, and fatty fish such as herring, salmon, and sardines. Other good choices are vitamin D-fortified foods such as milk, margarine, yogurt, and some cereals. In fact, fortified foods provide most of the vitamin D in the American diet. Just be sure to check the Nutrition Facts panel to ensure the food purchased is fortified with vitamin D. As we learned previously, vitamin D is known as the sunshine vitamin. The body can make vitamin D when sunlight or ultraviolent light hits human skin. Most people meet at least some of their vitamin D needs through exposure to sunlight. However, it s important to consume food sources of vitamin D, as well. Exposure to sunlight and radiation from tanning beds should be limited due to the risk of skin cancer. SLIDE #13: Rickets and osteomalacia are the classical vitamin D deficiency diseases. In children, vitamin D deficiency results in rickets. Rickets involves defective bone growth, which leads to soft bones and skeletal deformities. In adults, vitamin D deficiency leads to osteomalacia, or the softening of the bones. Fortification of milk with vitamin D virtually eliminated rickets in the United States. However, vitamin D deficiencies may become more prevalent if milk consumption continues to be replaced by juice and soda. SLIDE #14: Because vitamin D is fat-soluble and stored in the body, too much of it can be toxic, possibly leading to kidney stones or damage, weak muscles and bones, excessive bleeding, deafness, and other problems. An overdose of vitamin D is usually from dietary supplements, not from food or from overexposure to sunlight. SLIDE #15: Vitamin D intake through foods and supplementation is especially important in the following special populations. The vitamin D requirements for breastfed infants cannot ordinarily be met by human milk alone. Exclusively or partially breastfed infants should receive a vitamin D supplement. Breastfeeding mothers should check with their child s pediatrician about this issue. Older adults are at risk for deficiency because, as the human body ages, it is not able to synthesize vitamin D as efficiently. In addition, many older adults spend less time outdoors and experience less exposure to sunlight. People with limited sun exposure, such as those who are homebound, women who wear long robes and head coverings, or those with occupations that limit their sun exposure, may require a supplement. People with dark skin have greater amounts of melanin, which is the pigment that gives human skin its color. Darker skin reduces the skin s ability to synthesize vitamin D.

5 Vitamin D is fat-soluble and requires fat for absorption into the body. People with fat malabsorption may not be able to absorb sufficient amounts of vitamin D in their gut. Lastly, people who are obese or who have undergone gastric bypass surgery require higher amounts of vitamin D. Those recovering from surgery may not absorb adequate amounts of this vitamin. Section 7 Fat-Soluble Vitamins: Vitamin E SLIDE #16: Vitamin E is a fat-soluble vitamin and functions primarily as an antioxidant. Because vitamin E works as an antioxidant, it can help prevent the oxidation of LDL cholesterol, thus lowering the risk for heart disease, vascular disease, and stroke. In addition, vitamin E may help reduce the risk of cancer. SLIDE #17: As we just learned, the main function of vitamin E is to serve as an antioxidant. An antioxidant is a substance that can inhibit the reactions of damaging free radicals in the body. Free radicals cause oxidative stress, or damage to cells, which can lead to the development of cardiovascular disease and cancer. The main food sources of antioxidants like vitamin E are fruits and vegetables. SLIDE #18: Plant products are some of the richest sources of vitamin E. In particular, vegetable oils such as soybean, corn, cottonseed, safflower, and canola oil contain high amounts of vitamin E. Food products that contain oil, such as margarine and salad dressings, are also good sources. In addition, nuts such as almonds and hazelnuts, seeds such as sunflower seeds, and wheat germ are high in oil and are great sources of vitamin E. Other foods such as avocados, peanut butter, and egg yolks are also high in vitamin E. Some leafy, green vegetables like spinach contain vitamin E, but in smaller amounts. SLIDE #19: A deficiency in vitamin E is rare for most healthy people. However, very low-birthweight infants, those with cystic fibrosis, those with poor fat absorption, or those who consume a very low-fat diet can be at risk. SLIDE #20: Toxicity from too much vitamin E may lead to an increased risk of bleeding, impaired bone mineralization, and impaired vitamin A storage. Consuming large doses of vitamin E as a supplement does not conclusively have benefits, and it isn t recommended. Section 8 Fat-Soluble Vitamins: Vitamin K SLIDE #21: Vitamin K is a fat-soluble vitamin that plays a major role in proper blood clotting. In addition, it plays a role in the production of other important proteins related to the blood, bones, and the kidneys. Just like vitamin D, vitamin K can be produced by the body. Vitamin K is produced by bacteria that is found in the gut, but it can t be produced in sufficient amounts. SLIDE #22: The best food sources of vitamin K are green, leafy vegetables, including spinach, broccoli, cabbage, and dark lettuces. SLIDE #23: Except for rare medical conditions, a deficiency of vitamin K is rare. Individuals who are prescribed anticoagulant drugs, like coumarin, for example, may be at risk for deficiency because these drugs interfere with the vitamin K cycle. As a result, profuse bleeding or hemorrhaging may result if the person is injured. Prolonged use of antibiotics could also lead to a deficiency because they eliminate beneficial gut bacteria, which produce vitamin K.

6 Toxicity from too much vitamin K has few known effects. There have been some cases of vitamin K causing jaundice in infants. Section 9 Water-Soluble Vitamins: Folate SLIDE #24: Folate is a water-soluble B vitamin. Folic acid is the synthetic form of folate, which is found in supplements. Folate has several important functions, such as: promoting the proper growth and development of a fetus, which helps lower the risk of delivering a baby with neural tube defects like spina bifida; promoting proper DNA synthesis and new cell formation; and promoting proper formation of red blood cells. Specifically, folate works with vitamin B12 to form hemoglobin in red blood cells. In addition, folate helps control plasma homocysteine levels, which are linked to an increased risk of cardiovascular disease. SLIDE #25: Let s take a moment to further discuss the differences between folate and folic acid. Folate, as mentioned previously, is the naturally occurring form of the vitamin. Folate is only about 50% bioavailable, which means that the human body absorbs only about 50% of the folate that is present in food. Folic acid is the synthetic form of the vitamin. It is often added to foods or is available in dietary supplements. The bioavailability of folic acid is greater than 90%, and that s why it s used as a supplement and to fortify foods. SLIDE #26: Leafy green vegetables, such as spinach and turnip greens, citrus fruits, and dried beans and peas are all natural sources of folate. Some examples of foods include orange juice, lentils, dried beans, spinach, broccoli, peanuts, and avocados. In addition, many products including breakfast cereals, flour, bread, rice, and pasta are fortified with folic acid. Check the Nutrition Facts panel to determine if a food is fortified with folic acid. Many whole-grain foods are not fortified with folic acid. SLIDE #27: A deficiency in folate can affect normal cell division and protein synthesis, which will impair growth. Pregnant women, who do not take in adequate folate especially during the first tri-mester, have an increased risk of delivering a baby with a neural tube defect, which is a birth defect of the brain and spine. Spina bifida is an example of a neural tube defect. Because folate is needed for the formation of hemoglobin in red blood cells, a deficiency may also result in anemia. However, consuming too much folate can sometimes mask the symptoms of anemia from a vitamin B12 deficiency. SLIDE #28: Neural tube defects tend to be more prevalent among infants of Hispanic women. However, due to the special role folate plays in the prevention of neural tube defects, there are special recommendations regarding folate and folic acid consumption among pregnant women and those who may become pregnant. In fact, it is recommended that all women of childbearing age consume 400 micrograms of folic acid per day. During pregnancy, women should consume at least 600 micrograms of folic acid per day. Pregnant women should consult with their doctor.

7 Section 10 Water-Soluble Vitamins: Vitamin B12 SLIDE #29: Vitamin B12, which is also known as cobalamin, is a water-soluble vitamin with several important functions that include: the development of red blood cells, proper nerve function, proper cognitive performance, and proper metabolism and DNA synthesis. Some studies suggest that vitamin B12 may help prevent coronary artery disease, stroke, vascular disease, and blood clots. SLIDE #30: Vitamin B12 is only found in animal foods such as meat, poultry, fish, shellfish, eggs, milk, and cheese. It may also be found in fortified foods, such as some breakfast cereals. Strict vegetarians who eat no animal products, as well as the infants of vegan mothers, are at risk for a vitamin B12 deficiency. Consumption of vitamin B12-fortified foods or the use of supplements for these individuals is very important. SLIDE #31: Let s take a moment to discuss the digestion and absorption of vitamin B12. First, hydrochloric stomach acid and intrinsic factor are needed for vitamin B12 absorption. Intrinsic factor is a specific binding protein that is produced by the stomach. Intrinsic factor binds to vitamin B12 in the stomach. Then the intrinsic factor and vitamin B12 complex is absorbed into the body via the ileum of the small intestine. Interestingly, although vitamin B12 is water soluble, healthy people are able to store 5 to 7 years worth of vitamin B12 in their liver. SLIDE #32: Before we discuss the specific symptoms of a deficiency in vitamin B12, let s discuss several factors that may place an individual at risk for such a deficiency. These factors include: having a poor diet; being a strict vegan, who doesn t consume any type of animal products; having decreased stomach secretions, which causes decreased absorption; having bacterial overgrowth in the small intestines that results in less absorption; having a parasite; having an injury or surgery on part of the stomach or small intestine; having a gastroectomy; having decreased pancreatic secretions; and the lack of intrinsic factor, which results in pernicious anemia. SLIDE #33: A deficiency of vitamin B12 can result in anemia, fatigue, weakness, constipation, loss of appetite, and weight loss. Additional symptoms include nerve damage, depression, confusion, dementia, poor memory, a smooth tongue, and very sensitive skin.

8 Let s take a moment to further talk about anemia. Anemia is a shortage in the number or size of red blood cells, which results in a lower amount of oxygen being available to the body cells. There are two types of anemia associated with vitamin B12 deficiency: megaloblastic and pernicious. Megaloblastic anemia is a blood disorder in which the body produces larger than normal red blood cells. It is caused by a deficiency of folate or vitamin B12. Sometimes, this type of anemia can be masked if large doses of folic acid are administered. However, these large doses do not correct the neurological damage that also occurs as a result of the deficiency in B12. Pernicious anemia results when the body cannot properly absorb vitamin B12 from the gastrointestinal tract due to a lack of intrinsic factor. Some people may not make intrinsic factor because of genetic or medical reasons. Pernicious anemia can be effectively treated with injections of vitamin B12. There are no known symptoms or conditions from consuming excess vitamin B12. SLIDE #34: As we ve alluded to, several populations tend to have a higher prevalence of anemia. These populations include pregnant women and women of child-bearing age, vegetarians who are especially strict vegans, and the elderly. On average, most adults over age 50 consume adequate vitamin B12. However, many older individuals may have a reduced ability to absorb naturally occurring vitamin B12. In fact, the 2010 Dietary Guidelines for Americans suggests that individuals ages 50 and older should include foods fortified with vitamin B12, such as fortified cereals, or take dietary supplements. Section 11 Water-Soluble Vitamins: Vitamin C SLIDE #35: Vitamin C is also known as ascorbic acid. It is a water-soluble vitamin with several important functions, including: serving as an antioxidant; helping the body to absorb iron from plant sources of food; boosting immunity by protecting from infection and stimulating the formation of antibodies that fight infection; helping to heal wounds; helping to keep gums healthy; reducing bruising by keeping capillary walls and blood vessels firm; and synthesizing collagen, which is a connective tissue that hold muscles, bones, and other tissues together. SLIDE #36: Vitamin C mainly comes from plant sources of food. Choose a variety of fruits and vegetables. All citrus fruits, including oranges, grapefruits, and tangerines, are good sources. Other fruits such as kiwi and strawberries are also high in vitamin C. Dark green vegetables such as spinach, bell peppers, collards, and broccoli as well as tomatoes and potatoes are also good sources of vitamin C. Whenever possible, choose fresh and frozen produce since processing, heat, and oxygen can easily destroy vitamin C.

9 SLIDE #37: A severe deficiency of vitamin C will lead to scurvy. Scurvy is a disease that causes loose teeth, swollen gums, as well as bleeding around the gums, nails, and hair follicles. Individuals suffering from a vitamin C deficiency may also suffer from anemia, fatigue, poor wound healing, and joint and/or bone pain. If left untreated, scurvy is fatal. Thankfully, vitamin C deficiency is rare in the United States. SLIDE #38: Vitamin C is a water-soluble vitamin, and any additional amount above what the body needs will be excreted into the urine. In some cases, high doses of vitamin C in urine can mask the results of tests for diabetes. Very high doses of vitamin C may cause kidney stones, in addition to GI distress and diarrhea. Vitamin C is the most commonly used and overdosed supplement. Section 12 Supplement Use SLIDE #39: Approximately one-third of Americans take a multivitamin and/or mineral supplement. Taking this type of supplement can assist people with meeting certain nutrient requirements. However, no multivitamin or mineral supplement can take the place of eating a variety of healthful foods. However, certain groups of individuals might benefit from a multivitamin and/or mineral supplement. Let s talk about each of these groups. Women who might become pregnant should get 400 mcg/day of folic acid from fortified foods and/or dietary supplements to reduce the risk of birth defects of the brain and spine in their newborn babies. Pregnant women should take an iron supplement as recommended by their health care provider. A prenatal multivitamin or mineral supplement is likely to provide iron. Breastfed and partially breastfed infants should receive vitamin D supplements of 400 International Units, or IU, each day, as should non-breastfed infants who drink less than about 1 quart per day of vitamin D-fortified formula or milk. In postmenopausal women, calcium and vitamin D supplements may increase bone strength and reduce the risk of fractures. People over age 50 should get the recommended amounts of vitamin B12 from fortified foods and/or dietary supplements because they might not absorb enough of the B12 that is naturally found in food. Individuals considering the use of a supplement should first consult their doctor. The doctor or health care provider can help determine if a supplement is needed and which kind.

10 Let s do a quick activity. Section 13 Activity Take a look at the handout entitled Multivitamin/mineral supplements QuickFacts from the Office of Dietary Supplements. 1. Review the section entitled Should I take an MVM? on page 2 of the handout. 2. Take a moment and consider whether or not you fit any of these categories. 3. Do you need to talk with your doctor about a multivitamin/mineral supplement? Section 14 Summary SLIDE #40: This concludes our module on vitamins. Today we have discussed information about the fat-soluble vitamins A, D, E, and K. We also learned about key water-soluble vitamins including folate, vitamin B12, and vitamin C. In addition, we discussed key food sources for each of these vitamins and disease conditions related to deficiency and toxicities, if applicable. Thank you again for choosing Nutrition Essentials. You are now ready to complete the postlearning assessment. Section 15 References and Additional Resources To learn more about the topics we discussed today, visit the websites and resources below: Complete Food and Nutrition Guide. American Dietetic Association. Larson-Duyff R. 3 rd Edition. Dietary Guidelines for Americans, Krause s Food and the Nutrition Care Process. Mahan LK, Escott-Stump S, and Raymond JL. 13 th Edition. Office of Dietary Supplements National Institutes of Health. Vitamin and Mineral Supplement Fact Sheets. This module was developed by: Amanda R. Scott, MS, RD, LD Program Specialist Texas AgriLife Extension Service Texas A&M University System 2012 Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, age, or national origin. The Texas A&M University System, U.S. Department of Agriculture, and the County Commissioners Courts of Texas Cooperating